This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Application No. 2002-314306 filed on Oct. 29, 2002, the entire content of which is incorporated herein by reference.
This invention generally relates to a bumper apparatus for vehicle. More particularly, the present invention pertains to a bumper apparatus for vehicle including an improved bumper reinforcement.
Known bumper apparatuses, assembled to the front and/or the rear portions of the vehicle, include bumper reinforcements extending in vehicle width direction for absorbing an impact energy transmitted to the vehicle body as much as possible for minimizing a damage to driver upon vehicle collision at the front portion or the rear portion of the vehicle. The bumper apparatuses assembled to the front and/or the rear portions of the vehicle include energy absorbers made of elastic material (urethane form etc.) which mainly serve as protecting a pedestrian, bumper reinforcements supporting the energy absorbers and being adapted to deform their shapes for absorbing the large impact energy, and crush boxes or bumper stays for fixing the bumper reinforcements to vehicle body members (e.g. side members).
The bumper reinforcement has much contribution to absorbing the large impact energy upon vehicle collision at the front portion or the rear portion of vehicle.
The bumper reinforcement is made by extruding the aluminum base alloy material instead of steel material to lighten the weight of the vehicle for improving fuel economy. An example of such known bumper apparatus is disclosed in the Japanese Unexamined Patent Publication No. H(Heisei) 7-215146.
The known bumper reinforcement made of extruded aluminum base alloy material to be shaped in cross-section having two separated vertical portions and upper, intermediate and lower horizontal ribs of same thickness provided therebetween. Each end of the upper, intermediate and lower horizontal ribs is connected to upper portions, middle portions and lower portions of the vertical portions respectively.
The known bumper apparatus, wherein the bumper reinforcement is fixed to the side member of the vehicle side through the intermediate plate members, absorbs the impact energy upon vehicle collision by buckling to deform the three horizontal portions (ribs) equally and at the same time.
As described above, the bumper reinforcement including three horizontal portions (ribs) of the same thickness absorbs the impact energy upon vehicle collision by buckling to deform the three horizontal portions (ribs) at the same time, however, a load curve relative to stroke significantly decreases as the bumper reinforcement moves toward the end of the buckling movement. Thus, this configuration shows poor efficiency of absorbing impact energy.
To improve the inefficiency, thicknesses of each portion of the bumper reinforcements may be enhanced, however, thicker bumper reinforcement is unfavorable due to causing increasing in vehicle weight and decreasing in fuel efficiency.
Accordingly, it is an object of the present invention to solve these problems of the aforementioned know embodiment.
According to the current invention, a bumper apparatus for vehicle comprises a bumper reinforcement made by extruding an aluminum base alloy material to be shaped in cross-section having two separated vertical portions and upper, intermediate and lower horizontal ribs provided therebetween. Each one end of the upper, intermediate and lower horizontal ribs are connected to an upper portion, a middle portion and a lower portion of one of the vertical portions respectively, and each the other end of the upper, intermediate and lower horizontal ribs are connected to an upper portion, a middle portion and a lower portion of the other of the vertical portions respectively. In this configuration, the thickness of the intermediate rib is set to be 1.2-2.0 times thicker than the thicknesses of the upper rib and the lower rib which have the same thickness. A crush box is fixed to the vehicle body, and one side surface of the bumper reinforcement is fixed to the crush box through an intermediate plate provided therebetween. Thus, an impact energy is absorbed by deforming the upper rib and the lower rib, the intermediate plate member, the crush box in order, and finally the intermediate rib.